A variety of tumor-associated glycoproteins and glycolipids carrying X determinant [Gal.beta.1.fwdarw.4(Fuc.alpha.].fwdarw.3)GlcNAc] and sialylated X determinant structures have been reported. Some of these glycoconjugates contain repetitive 3-fucosyllactosamine (X determinant) units. For example, the fucolipid, Gal.beta.1.fwdarw.4(Fuc.alpha.1.fwdarw.3)GlcNAc.beta.1.fwdarw.3Gal.beta.1. fwdarw.4(Fuc.alpha.1.fwdarw.3)GlcNAc.beta.1.fwdarw.4Gal.beta.1.fwdarw.4Glc. beta.1.fwdarw.Cer, has been isolated from human colonic and liver adenocarcinoma by Hakomori and co-workers. These investigators have recommended the need for isolation of hybridoma producing a monoclonal antibody which should specifically recognize the internal fucosyl sequence, Fuc.alpha.1.fwdarw.3GlcNAc.beta.1.fwdarw.3Gal.beta.1.fwdarw.4(Fu c.alpha.1.fwdarw.3)GlcNAc.beta.1.fwdarw.3Gal, and not the external X determinant, because, such an antibody would be unique in detecting structures specific for human cancer. A closer look at many of these tumor associated fucosyl glycoconjugates reveals that the X determinant is attached at either the C-6 position of D-GalNAc, D-Man and D-Gal; the C-2 of D-Man or the C-3 position of D-Gal.
It is well known in the art that the use of a hexopyranosyl glycosyl donor having a "nonparticipating" group at the O-2 position has resulted in high yields of .alpha.-linked oligosaccharides. For .alpha.-L-fucosylation of an appropriately protected acceptor, glucosylating reagents such as: methyl 1-thio-2,3,4-tri-O-benzyl-.beta.-L-fucopyranoside, 2,3,4-tri-O-benzyl-.beta.-L-fucopyranosyl fluoride; 2,3,4-tri-O-benzyl-.alpha./.beta.-L-fucopyranosyl trichloroacetimidate and 2,3,4-tri-O-benzyl-.alpha.-L-fucopyranosyl bromide, under halide ion catalyzed conditions have been used.
When the synthesis of .alpha.-L-fucopyranosyl oligosaccharides are desired, the literature has focused upon methyl 1-thio-2,3,4-tri-O-benzyl-.beta.-L-fucopyranoside, 2,3,4-tri-O-benzyl-.beta.-L-fucopyranosyl fluoride, and 2,3,4-tri-O-benzyl-.alpha./.beta.-L-fucopyranosyl trichloroacetamide as the glycosylating agents of choice. Each of the above glycosylating reagents employ O-benzyl protection which necessitates hydrogenolysis for removal.